Smoke is generated for a number of applications, including military screening of areas, theatrical effects, and training of fire fighters, among others. The present invention relates to these usual applications for smoke generation, but it is particularly useful where the generation of the smoke must be closely controlled. As an example thereof, when smoke is used for training fire fighters, the training environment, e.g. a training chamber, is arranged such that when the trainee properly applies the correct extinguishing agent, at the correct position of a simulated fire and for the correct length of time, the simulated fire is extinguished, and the simulated smoke associated therewith is likewise extinguished. On the other hand, for example, if the trainee does not apply the extinguishing agent for the correct length of time, even though the simulated fire and smoke are discontinued, a "flashback" or "burnback" of sudden reignition is simulated by an immediate burst of simulated fire and smoke. Thus, as opposed to other applications, such as theatrical applications, where the commencement and discontinuance of the smoke in very short periods of time is not necessary, for purposes of training fire fighters, such commencement and discontinuance in a very short period of time is most desirable, in order to realistically represent actual fire conditions for the trainee.
Smoke generation is usually achieved by vaporizing a smoke-generating fluid and mixing that vaporized fluid with air such that an aerosol fog of the vaporized and at least partially condensed smoke-generating fluid is produced. As can be appreciated, therefore, in order to generate smoke from a smoke-generating fluid, the apparatus and methods utilized must heat the smoke-generating fluid to a temperature sufficient to cause substantial vaporization thereof and, at the same time, mix the vaporized smoke fluid with air to provide the aerosol fog of the vaporized and condensed smoke fluid. However, as can also be appreciated, heating the smoke fluid to temperatures sufficient to cause substantial vaporization for smoke-generating purposes and then cooling that fluid to temperatures such that substantial generation of vapor and smoke does not occur, in a very short period of time, poses a considerable difficulty in the art.
Basically, in the prior art, smoke has been produced in one of several manners. First, a hot gas, usually air, is passed in contact with smoke-generating fluid, which may be in either a heated or unheated condition. The hot air causes vaporization of the smoke fluid into the air, and, with cooling, the desired fog results. However, as can be appreciated, if hot air is used to heat the smoke fluid, a considerable time lapse is required for enough hot air to pass in contact with the smoke fluid to cause sufficient heating of the fluid and generation of substantial amounts of vapor therefrom. Therefore, there is a slow and gradual buildup of vaporized smoke fluid in the hot air, and, as a result, there is, correspondingly, a slow and gradual buildup of the fog so produced. This, of course, would be most unsatisfactory for fire fighter trainees, since this would not duplicate actual fire fighting experiences.
Another method is that of heating a pool of smoke fluid to a temperature sufficient that substantial vapors therefrom are produced, and then blowing air, heated or unheated, over the fluid to cause the desired smoke. However, as can be appreciated, in this method, again, during the time period required to sufficiently heat the pool of smoke fluid and the time period required for cooling the pool of smoke fluid, the density of the smoke produced will slowly increase and then slowly decrease, respectively, which, again, is not a realistic representation of actual fire fighting conditions.
Another method in the art is that of atomizing the smoke fluid and forming an aerosol thereof directly in a forced air stream, which may or may not be heated. However, the smoke produced by this method, being relatively cold, has a density greater than air, and rather than the smoke rising, for example in a room, so as to simulate the actual effect of smoke from a fire, the smoke settles toward the floor of that room and gives the appearance of a theatrical effect, rather than a fire effect. This, of course, is totally unacceptable for training fire fighters.
Another method in the art admixes steam with the smoke fluid to produce vapors thereof, and then forces that mixture through narrow orifices into the atmosphere where the steam and vapor are chilled to produce smoke. Here again, the rising effect of smoke in actual fires is not duplicated.
Conventional smoke bombs have also been used for this purpose, but they are not controllable, since once the bomb is exploded, it continues to produce smoke, unabated, until the smoke fluid is depleted.
Representative of the above briefly discussed prior art are U.S. Pat. Nos. 4,439,341; 4,547,656; 4,568,820; 4,764,660; and 4,818,843.
Recently, it has been proposed in the art to provide a vaporizing unit for the smoke fluid where the smoke fluid passes between interior walls and exterior walls of a vaporizing chamber, where the passageway between the walls is narrow such as to produce a very high surface area of walls/volume of fluid ratio. By this means, smoke fluid can be rapidly heated to produce vapors thereof, and then those vapors are expelled into the atmosphere for producing the desired smoke (see U.S. Pat. No. 4,871,115). However, this apparatus has several distinct disadvantages. Firstly, there is a considerable thermal lag in heating and cooling the chamber, with a corresponding lag in the commencement and discontinuance of smoke. Secondly, the narrow passageway between the interior walls and the exterior walls of the vaporizing chamber can be clogged by residues and thermal degradation products of the smoke fluid when heated to vaporization temperatures. This cause unevenness and discontinuities in the vapors produced and, hence, in the smoke produced. Further, the smoke is produced by passing the heated vapors to ambient air, for cooling purposes, and that smoke, of course, as explained above, will be more dense than air and will, therefore, settle. This device is, therefore, very useful for producing theatrical effects, but is not particularly useful for fire fighter training.
A substantial improvement in generating smoke is disclosed in copending application Ser. No. 07/707,868 filed May 31, 1991, commonly assigned, wherein the smoke can be very quickly established or discontinued, and without the problems of the prior art, as recited above, and especially without the problem associated with U.S. Pat. No. 4,871,115, as discussed above. In that copending application, there is disclosed an apparatus for generating smoke from a smoke-generating fluid, wherein a chamber is provided that has a center line between an outlet wall and an inlet wall that is inclined to the horizontal. A particular surface is provided on the lowermost portions of the walls of that chamber, and smoke-generating fluid is flowed from a distribution means at the inlet wall to the outlet wall by gravity. This creates a very thin film of the smoke-generating fluid, and by use of heaters associated with the chamber, that thin film can be very quickly raised to temperatures sufficient to cause substantial vaporization, or quickly lowered to below those temperatures, in order to quickly commence or discontinue generation of the vapor. Vaporized fluid is ejected from the chamber and mixed with heated air. By the combination of the quick generation and discontinuance of vapor and the commencement and discontinuance of ejecting the vapors, smoke can be very quickly started or stopped.
It has been found in practice, however, that this apparatus suffers from some disadvantages in some circumstances. Notably, and particularly in regard to certain smoke-generating fluids, the flow of the fluid in the chamber, as caused by gravity in view of the inclination of the chamber to the horizontal, is not as uniform as would be desired. This is because certain conventional smoke-generating fluids tend to channel on the heated surface of the lowermost portion of the chamber, and the heating and discontinuance of heating of the fluid, with such channeling, is not as quick or efficient as desired.
Further, residues of some smoke-generating fluid tend to collect on the roughened lower vaporization surface because these residues are not flushed from that roughened surface by subsequent flows of that fluid. Thus, somewhat frequent disassembly and cleaning of that device is required.
Further, the size of the device must be relatively large for producing large volumes of dense smoke, and this large size is undesired for some fire-fighting trainer facilities.
It would, therefore, be of substantial advantage in the art to provide an apparatus and method for controllably generating smoke, where that smoke has the same rising characteristics as smoke produced from fires, where that smoke can be quickly commenced and quickly discontinued and where these advantages can be provided with almost any smoke-generating fluid in a highly efficient manner, without channeling or requiring frequent cleaning and in a compact apparatus. It would be a further advantage in the art to provide for such smoke generation by use of relatively modern smoke fluids which have less toxicity and less potential for ignition than older smoke-generating fluids.